1. Field of the Invention
This invention relates to a recording head comprising a recording element substrate having a recording element formed thereon and a driving element substrate having formed thereon a driving element for driving the recording element in accordance with an image signal inputted from outside, the two substrates being in pressure contact with each other, a head cartridge integrally having the head and a storing portion for storing therein ink to be supplied to the head, and a recording apparatus on which the head is mounted.
2. Related Background Art
FIGS. 6A and 6B of the accompanying drawings show an example of the structure of a recording element unit in a recording head according to the prior art, FIG. 6A being a schematic structural view, and FIG. 6B being a cross-sectional view showing a cross-section 6B--6B shown in FIG. 6A.
This example of the prior art, as shown in FIGS. 6A and 6B, is comprised of an HfB.sub.2 layer 1502 as a heat generating resistance layer generating heat energy by an electric current flowing therethrough, individual electrodes 1504 of A1 and pattern wiring 1505a of A1 for the supply of electric current from outside to the HfB.sub.2 layer 1502, pattern wiring 1505b of A1 and a common electrode 1503 for causing the electric current supplied to the HfB.sub.2 layer 1502 to flow out, a Ta layer 1508 as a cavitation resisting layer, an SiO.sub.2 layer 1506 as an oxidation resisting layer and an insulating layer, a photosensitive polyimide layer 1507 as an oxidation resisting layer and an insulating layer, and a holding member 1501 holding these parts.
In the recording element unit constructed as described above, when an electric current for driving the recording element flows from outside, this electric current flows into the HfB.sub.2 layer 1502 through the individual electrodes 1504 and the pattern wiring 1505a, and further flows to the outside through the pattern wiring 1505b and the common electrode 1503, whereby heat energy is generated in the HfB.sub.2 layer 1502. By the generated heat energy, liquid is discharged and recording on a recording medium is effected.
Also, in the combination of the HfB.sub.2 layer 1502, the individual electrodes 1504 and the pattern wirings 1505a, 1505b as described above (hereinafter referred to as the heat generating element), it is often the case that as shown in FIG. 6A, a plurality of heat generating elements are formed in a recording element unit.
When a plurality of heat generating elements are provided in a recording element unit, it becomes possible to provide an ink jet recording apparatus for effecting the recording of a plurality of dots at a time and therefore, higher speed of recording can be achieved. Particularly, in recent years, the demand for higher density and high-speed recording is great and it has been generalized to effect recording of one main scanning line at a time, and there has been the advent of a recording element unit in which a number of heat generating elements are disposed highly densely.
When as described above, a plurality of heat generating elements are disposed in a recording element unit and the recording of a plurality of dots is effected at a time, the ON/OFF of each of the heat generating elements must be individually controlled. However, means for effecting the ON/OFF control of the heat generating elements (hereinafter referred to as the driving element) can be formed in the recording element unit, but when it is formed on a substrate integral with the recording element in the recording unit, if a portion of one of the recording element and the driving element becomes bad, the entire recording unit may become inoperative and therefore, usually, the driving element is formed on an independent substrate (hereinafter referred to as the driving element substrate) and is connected to the recording element unit.
As a method of electrically connecting the substrate on which the recording element is formed and the driving element substrate together, there is a method disclosed in Japanese Patent Application Laid-Open No. 3-121851.
The method disclosed in Japanese Patent Application Laid-Open No. 3-121851 comprises forming bubble-like electrodes on the individual electrodes of a recording element having substantially the same construction as that shown in FIGS. 6A and 6B so as to be protuberant on the substrate, and joining the substrate on which the recording element is formed and the driving element substrate together by the crimp method.
Also, as another method of joining the substrate on which the recording element is formed and the driving element substrate together, there is a method disclosed in Japanese Patent Application Laid-Open No. 1-302829.
FIGS. 7A to 7C of the accompanying drawings illustrate an electrically connecting method for the recording element substrate and the driving element substrate disclosed in Japanese Patent Application Laid-Open No. 1-302829.
As shown in FIGS. 7A to 7C, in this example of the prior art, a driving element substrate 1705 having an electrode portion 1715 and insulating film 1719 and a recording element substrate 1704 having an electrode portion 1714 and insulating film 1720 are disposed in opposed relationship with each other through an electrical connecting member 1703 on which electrically conductive members 1717 are held by a holding member 1718 (FIG. 7A), and thereafter are brought into pressure contact with each other (FIGS. 7B and 7C), whereby the recording element substrate 1704 and the driving element substrate 1705 are joined together.
The arrangement pitch of the electrically conductive members 1717 is set more narrowly than the arrangement pitch of the electrode 1714 and the electrode 1715.
FIGS. 8A and 8B of the accompanying drawings show an example of the construction of the recording head of an ink jet recording apparatus according to the background art which comprises a recording element substrate and a driving element substrate brought into pressure contact with each other, FIG. 8A being a pictorial perspective view, and FIG. 8B being a side view.
This example, as shown in FIGS. 8A and 8B, is comprised of a driving element substrate 2002 on which a driving element 2003 is formed, a recording element substrate 2001 on which a recording element (not shown) is formed, a circuit substrate 2004 electrically connected to the driving element substrate 2002 by a method such as wire bonding, a base bed 2005 for holding down the driving element substrate 2002 and the circuit substrate 2004, a pressure contact plate 2007 bringing the driving element substrate 2002 and the recording element substrate 2001 into pressure contact with each other through the base bed 2005 and electrically connecting them together, an elastic member 2008 provided between the pressure contact plate 2007 and the base bed 2005, a top plate 2011 provided on that portion of the surface of the recording element substrate 2001 which is not in contact with the driving element substrate 2002, a holding plate 2006 for fixing the recording element substrate 2001 by a method such as adhesion, and holding down and aforementioned parts, a fixing screw 2010 for fixing the pressure contact plate 2007 and the base bed 2005, a spacer 2009 and a support post 2012.
Also, an ink liquid chamber (not shown) is disposed between the recording element substrate 2001 and the top plate 2011, and energy for ink discharge is supplied to the ink liquid chamber by the recording element on the recording element substrate 2001.
The recording head as described above is constructed by bringing the driving element substrate 2002 fixed to the base bed 2005 into pressure contact with the recording element substrate 2001 by the pressure contact plate 2007.
In the technical substance as described above, however, when the driving element substrate is to be brought into pressure contact with the recording element substrate, the pressure contact position of the driving element substrate with the recording element substrate is remote from the center of gravity of the base bed to which the driving element substrate is fixed and therefore, balanceability becomes bad during the pressure contact work and the work becomes difficult.
Therefore, there is provided a spacer for supporting the base bed on the holding plate to thereby improve the balanceability during the pressure contact work, but in the length of the spacer, the height of the surface of pressure contact between the recording element substrate and the driving element substrate must be made the same and thus, high accuracy is required.
Also, the length of the spacer must be adjusted correspondingly to the errors of the thickness of the recording element substrate, the accuracy of the adhesion between the recording element substrate and the holding plate, the inclination of the pressure contact surface of the recording element substrate, etc., and this leads to the problem that an increase in cost arises for the setting of the spacer.
Further, there is the problem that the reliability of the electrical connection in the pressure contact portion between the recording element substrate and the driving element substrate is reduced by an extraneous force created when a connector is connected to the circuit substrate for the supply of an outside signal.